A six-speed or seven-speed double clutch transmission is known from published patent DE 103 05 241 A1. The double clutch transmission comprises two clutches which are each connected by their input sides with the drive shaft and by their output sides with one of the two transmission input shafts. The two transmission input shafts are arranged coaxially relative to each other. Furthermore, two countershafts are arranged parallel to the axis of the two transmission input shafts, of which the idler gears engage with fixed gears of the transmission input shafts. In addition, coupling devices are held in a rotationally fixed manner and movable on the countershafts to be able to shift the corresponding toothed gearwheels. Each chosen transmission ratio is transmitted to a differential by means of the output gears. To realize the desired transmission ratio stages in the known double clutch transmission, a multiplicity of gear planes is necessary so that a not insignificant amount of construction space is needed for installation.
Furthermore, a spur-gear multi-speed transmission is known from published patent DE 38 22 330 A1. The spur-gear multi-speed transmission comprises a power shiftable double clutch of which one part is connected to a drive shaft and of which another part is connected to a hollow drive shaft which is fixed in a rotational manner on the drive shaft. The drive shaft can be coupled with the hollow drive shaft by means of a shift element for certain transmission ratios.
A power-shift transmission with two clutches is known from published patent DE 10 2004 001 961 A1, in which the clutches are assigned to a subtransmission. The transmission input shafts of the two subtransmissions are arranged coaxially relative to each other and mesh with idler gears of the assigned countershafts by means of fixed gears. Each idler gear of the countershafts can be connected in a rotationally fixed manner to one of the countershafts by means of assigned shift elements. From this published patent, an eight-speed transmission is also known for which another shift element is provided for coupling the two transmission input shafts for the realization of a further transmission ratio stage. Even the seven-geared transmission requires at least six gear planes in the two subtransmissions in this embodiment to be able to realize the transmission ratio stages. This leads to an undesirable lengthening of the construction length in the axial direction so that the possibility of installation in a vehicle is significantly limited.
Furthermore, another power shiftable transmission is known from published patent DE 10 2005 028 532 A1, which comprises two input shafts and only one countershaft. An eight-speed transmission in this embodiment, for example, requires more than seven gear planes to be able to realize the transmission ratio stages, especially the reverse gear transmission ratios. This leads to an undesirable lengthening of the construction length in the axial direction.